•DNA complexity can be quantified using entropy profiles.•Gene promoter complexity is influenced by non-random patterns in the DNA sequence.•Housekeeping (HK) and tissue specific (TS) gene promoters have different DNA entropy profiles.•TS promoters have lower DNA entropies than HK promoters.•Lower entropies of TS promoters can be explained by higher densities of regulatory elements.

BackgroundThe complexity of DNA can be quantified using estimates of entropy. Variation in DNA complexity is expected between the promoters of genes with different transcriptional mechanisms; namely housekeeping (HK) and tissue specific (TS). The former are transcribed constitutively to maintain general cellular functions, and the latter are transcribed in restricted tissue and cells types for specific molecular events. It is known that promoter features in the human genome are related to tissue specificity, but this has been difficult to quantify on a genomic scale. If entropy effectively quantifies DNA complexity, calculating the entropies of HK and TS gene promoters as profiles may reveal significant differences.ResultsEntropy profiles were calculated for a total dataset of 12,003 human gene promoters and for 501 housekeeping (HK) and 587 tissue specific (TS) human gene promoters. The mean profiles show the TS promoters have a significantly lower entropy (p